The two predominant topologies, known in prior art, and used for class-D amplifiers are the full-bridge- and the half-bridge topology.
For low cost consumer products the half-bridge topology has a distinct advantage over the full-bridge since only half the number of power switches, drivers and output inductors is needed. Even though the voltage rating of the power switches is doubled in the half-bridge topology, there is still a manufacturing and cost benefit due to the reduction of number of components. Since the speaker output terminals are referenced to ground, overload protection and output sensing becomes easier compared to the full-bridge topology.
The drawback of the half-bridge class-D topology is the need for a dual rail supply and the fact that this topology will pump current back to the opposite supply rail from where the power is being drained.
This problem is described in some detail in U.S. 2004/0145930, which is directed to a solution based on rectifiers in parallel with controlled switches.
A more efficient solution to the rail pumping problem is disclosed in US application 2009/0102295, assigned to the same assignee of the present invention. By this solution, the advantages of using a single-ended class D amplifier in consumer products have been made practically available.
The consumer product market requires very efficient audio amplifiers with a high output power which at the same time consumes as little power as possible.